The present invention relates to multilayer compositions comprising thermoprocessable fluoropolymers and hydrogenated polymers having improved adhesion among the single layers.
In particular the invention relates to multilayer compositions based on thermoprocessable fluoropolymers and A hydrogenated polymers, wherein the thermoprocessable fluoropolymers are copolymers of ethylene (E) with tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE). Said multilayer compositions show improved adhesion among the single layers and high chemical resistance.
The use of hydrogenated polymers in the car industry for preparing fuel hoses and fuel lines is known in the prior art. Examples of hydrogenated polymers are polyamides, polyvinylchloride (PVC), nitrile rubbers (NBR). The drawbacks of the manufactured articles obtained from said polymers are the low chemical resistance and high permeability to gasolines and oils, in particular SF oils. A high permeability to this fluids, in particular gasolines, implies a high emission of dangerous substances to the environment. The laws of most countries are more and more restrictive on these emissions due to their environmental impact. Therefore, manufactured articles having a lower permeability and an improved chemical resistance are required.
Fluorinated polymers are known, which, in comparison with hydrogenated polymers, have an improved chemical resistance to gasolines and to particularly aggressive oils used in the car industry. The drawback of fluorinated polymers is the high cost which limits the use thereof.
To make economically possible the use of fluorinated polymers it has been tried to laminate hydrogenated polymers with fluorinated polymers, for example in the preparation of fuel hoses (hydrogenated rubbers/fluorinated polymers) and fuel lines (polyamides/fluorinated polymers). However the adhesion between fluorinated polymers and hydrogenated polymers is very poor. The research is directed to find solutions such as to make it possible these laminates. This is true in particular for the thermoprocessable fluorinated copolymers of ethylene (E) with tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE), for example Halar(copyright) commercialized by Ausimont. Tests carried out by the Applicant, see the comparative Examples, have shown that the hydrogenated polymer/fluorinated polymer bilayer gives a poor adhesion or, in most cases, no adhesion among the layers of the manufactured article.
The need was therefore felt to make multilayer polymer manufactured articles having a high adhesion among the single layers, which contemporaneously show a high chemical resistance typical of fluorinated polymers and good mechanical properties when the hydrogenated polymers are thermoprocessable.
An object of the present invention is therefore a multilayer composition comprising:
A) a first layer based on copolymers of ethylene (E) with tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE), preferably CTFE;
B) a second intermediate layer based on thermoprocessable copolymers of ethylene (E) with tetrafluoroethylene (TFE) and/or chlorotrifluoroethylene (CTFE) modified with acrylic monomers of formula:
CH2xe2x95x90CHxe2x80x94COxe2x80x94Oxe2x80x94R2xe2x80x83xe2x80x83(a)
R2 is a C1-C20 hydrogenated radical from 1 to 20 carbon atoms, linear and/or branched alkyl radical or cycloalkyl radical, or R2 is H. The R2 radical can optionally contain: heteroatoms preferably Cl, O, N; one or more functional groups preferably selected from OH, COOH, epoxide, ester and ether;
C) a third layer based on hydrogenated polymers;
said multilayer composition containing in layer B) and/or in layer C) one or more crosslinking agents of fluorinated polymers.
The copolymers of layer A) contain:
from 30 to 60% by moles, preferably from 40 to 50% of ethylene;
from 40 to 70% by moles, preferably from 50 to 60% of a fluorinated monomer selected from tettafluoroethylene, chlorotrifluoroethylene, or mixtures thereof;
optionally from 0.1 to 5% by moles referred to the sum of the previous monomers of a fluorinated monomer selected from perfluoroalkylvinylethers, preferably perfluoropropylvinylether (PPVE), perfluorodioxoles, hexafluoroisobutene.
The thermoprocessable copolymers of layer B) are formed by:
from 10 to 70% by moles, preferably from 35 to 55% of ethylene;
from 30 to 90% by moles, preferably from 45 to 65%, of a fluorinated monomer selected from tetrafluoroethylene, chlorotrifluoroethylene, or mixtures thereof, preferably CTFE;
from 0.1 to 30% by moles, preferably from 1 to 15% by moles of the acrylic comonomer (a) referred to the sum of the previous monomers.
The acrylic monomers of formula (a) are preferably n-butylacrylate.
Optionally layer B) comprises also the thermoprocessable copolymers of layer A) in an amount from 0 to 95% by weight, preferably from 70 to 95% by weight with respect to the copolymers of layer B), with the proviso that layer B) contains an amount of acrylic monomers of formula (a) of at least 0.1% by moles. It has been found by the Applicant that when in layer B) a blend of the copolymers of A) and B) is used and the final amount of the comonomer of formula a) in the blend is lower than 0.5% by moles, then the multilayer can be made without using layer A), yet substantially maintaining the multilayer properties.
The hydrogenated polymers of layer C) are of both thermoprocessable and elastomeric type, preferably thermoprocessable. Among thermoprocessable polymers, hydrocellulose polymers, polyamides as NYLON 6, NYLON 66, NYLON 11, NYLON 12, polyamide copolymers, polycarbonates, polyesters, such as for example polyethylenterephthalate, polyolefins such as for example high and low density polyethylene, olefine copolymers, polyimides, polystyrene, polyurethanes, polyvinylchloride (PVC), polysulphones, ethylene/vinylacetate copolymers, polyacrylobutadienestyrene (ABS), can be mentioned.
As hydrogenated elastomers we can mention acrylic rubbers, nitrile rubbers (NBR), ethylene-propylene rubbers (EPM), ethylene-propylene-diene rubbers (EPDM), NVC rubbers (nitrile NBR rubbers mixed with PVC), epichloro-hydrin rubbers (CO and ECO).
The preferred thermoprocessable hydrogenated polymers are polyesters, polyolefins, polyamides.
The preferred hydrogenated elastomers are epichlorohydrin and nitrile rubbers (NBR).
The crosslinking agents used in the multilayer composition of the invention can be of both radical and ionic type and they are those well known and conventionally used in the crosslinking of fluorinated polymers.
As radical crosslinking agents we can mention triallylisocyanurate (TAIC), triallylcyanurate (TAC), diallylisophthalate (U.S. Pat. No. 4,039,631), diallylterephthalate (U.S. Pat. No. 4,039,631), esters of phenyl indan (U.S. Pat. No. 3,763,222), triallylester of the aryl polycarboxylic acid (U.S. Pat. No. 3,840,619), bis-olefins such as for example 1,6 divinylperfluorohexane (see U.S. Pat. No. 5,612,419) and others (see U.S. Pat. No. 4,121,001). Among the radical crosslinking agents, triallylisocyanurate is preferred. Preferably the radical crosslinking agent is used in combination with a peroxide, for example Luperco(copyright) 101 XL (2,5-dimethyl-2,5-di(terbutylperoxy)hexane 45% by weight based on inert support), dicumylperoxide and terbutylhydroperoxide. In this case when the peroxide is present in layer C), the crosslinking agent is present in layer B), or viceversa.
As ionic crosslinking agents, we can mention those of amine type, for example hexamethylendiaminecarbamate, N,Nxe2x80x2-dicinnamylidene-1,6 hexanediamine, maleimides derivatives, such for example m-phenylenbismaleimide, C4-C20 aliphatic diamines, or polyhydroxyl aromatic compounds, for example bisphenols, A, AF and S, preferably in combination with a crosslinking accelerator, for example ammonium or phosphonium salts, preferably tetralkyl salts, for example tetrabutyl or phosphoranamines salts. In this case when the polyhydroxyl aromatic compounds are present in layer C), the accelerator is present in layer B), or viceversa. Preferably the accelerator is in layer C). The molar ratio between the accelerator and the polyhydroxyl aromatic compounds generally ranges between 1:5 and 1:1.
Among the ionically active crosslinking agents, both aliphatic and aromatic protected diamines are preferred. Preferably amines are used in layer C).
The crosslinking agent amount can range from 0.1 to 20.0% by weight, preferably from 0.5 to 10.0% by weight, more preferably from 1.0 to 5.0% by weight with respect to the polymer.
The multilayer compositions of the invention can furthermore contain one or more optional ingredients such as fillers (for example polytetrafluoroethylene (PTFE), silicates), xe2x80x9csmoke retardersxe2x80x9d, lubricants, pigments, xe2x80x9cfire retardantsxe2x80x9d, xe2x80x9cintumescent agentsxe2x80x9d, plasticizers (for example MORFLEX(copyright) 560), metal oxides (ZnO, MgO), inorganic bases (Ca(OH)2), thermal stabilizers such as for example Irganox(copyright) 1010.
The maximum total amount of said optional components is in the range 0 and 30% by weight.
The multilayer composition of the present invention can be obtained by co-extrusion of layers A), B) and C). An alternative method is the compression of the single layers at the softening temperature of the components. Preferably the co-extrusion method is used.
From the multilayer compositions of the invention manufactured articles are obtained, for example fuel lines obtained by co-extrusion of polyamide (layer C) and of layers A) and B) of the invention, fuel hoses obtained for example by extrusion of a hydrogenated rubber (layer C) on a tube formed by co-extruded layers A) and B).
The multilayer manufactured articles A/B/C obtainable from the compositions of the invention show the following combination of properties:
high chemical resistance when in contact layer A) of the multilayer with aggressive fluids;
good mechanical properties;
very good adhesion among the single layers, wherefore the manufactured articles are completely integrated.
Some embodiment examples of the present invention are hereinafter reported, the purpose of which is merely illustrative but not limitative of the scope of the invention itself.